A conventional bearing to support a camshaft of a car engine is disclosed in Japanese Unexamined Patent Publication No. 2005-180459, for example. Referring to FIG. 21, a camshaft 101 disclosed in the document has a cam lobe 101a, a cylindrical journal part 101b to be supported by a roller bearing 102, and a large-diameter end part 101c. 
Here, an outer diameter dimension of the journal part 101b is smaller than a maximum dimension of an outer diameter of the cam lobe 101a and an outer diameter dimension of the large-diameter end part 101c. Therefore, the roller bearing 102 to be arranged at the journal part 101b to support the camshaft 101 rotatably cannot be inserted from an axial direction of the camshaft 101.
Thus, the roller bearing 102 has a plurality of rollers 103, roughly semi-cylindrical retainers 104 and 105 split in a circumferential direction, and roughly semi-cylindrical race plates 106 and 107 arranged between a cylinder head 108 and a cap 109 and split in the circumferential direction.
The race plates 106 and 107 have projections 106a and 107a, respectively each projecting from axial each end face of a circumferential center part toward a radial outer side. Meanwhile, the cylinder head 108 and the cap 109 are provided with recess parts 108a and 109a to receive the projections 106a and 107a of the race plates 106 and 107, respectively. Thus, it is reported that when the projections 106a and 107a engage with the recess parts 108a and 109a, respectively, the circumferential and axial movements of the race plates 106 and 107 are prevented.
In addition, referring to FIG. 22, one circumferential side end of the race plate 106 is a wedge-shaped projection part 106b, and the other circumferential side end thereof is a valley-shaped recess part 106c. In addition, circumferential both ends have been pressed. Thus, it is reported that since a burr generated at the circumferential end due to the punching process is corrected and an end configuration is also corrected, assembling accuracy is improved.
Furthermore, the above race plates 106 and 107 are produced from a steel plate such as cold rolled steel plate (SPC) by a press process in general. In addition, a heat treatment is performed to obtain predetermined characteristics such as hardness, and a grinding process is performed on the inner diameter surface serving as a track surface of the roller 103, so that the roller 103 can rotate smoothly.
According to the above document, although the direction of the press performed on circumferential both ends of the above race plate 106 is not described, it is contemplated that the press process is performed in a direction (shown by arrows in FIG. 22) perpendicular to an outline in view of the purpose to correct the burr and the purpose to correct the end configuration.
However, since the part pressed in the above direction is inclined from the rolling direction of the roller 103 to the left or right, the behavior of the roller 103 could be hindered by the pressed part when the roller 103 passes through an abutment part between the race plates 106 and 107.
In addition, since a load biased in a predetermined direction is applied to the camshaft 101 at the time of rotation, the above camshaft support structure is sectioned to a region to which a relatively high load is applied (referred to as the “load region” hereinafter), and a region to which a relatively low load is applied (referred to as the “non-load region” hereinafter).
Therefore, since the high load is applied to the race plate positioned in the load region, high process accuracy is required in order to maintain the smooth rotation of the roller 103. Meanwhile, since many steps are required to produce the race plate as described above, the production cost of the race plate represents a major proportion of overall production cost of the roller bearing 102. This becomes considerably noticeable especially when high-accuracy process is needed.